Is this a clear Oring that came from inside the valve? Next to the washer. You need to fix it. That Oring holds the washer in place against the tombstone. You can fix it from the outside. Use a small screwdriver (flat) or something with a curve at the end to place it back in the hole. As the saying goes "washer first then the O ring". Use your pinky finger to make sure it all sits flat in the hole.

I have yet to have any broken or missing parts fix themselves by charging it up and firing.